Drip irrigation systems have come into widespread use in the agricultural area. Drip irrigation systems supply water at a slow, controlled rate to the root zone of the particular plants being irrigated. Typically, drip irrigation is accomplished by providing a low volume water outlet at each plant that permits a limited dripping of water directly to the root zone of the particular plant. Because evaporation, runoff, overwatering, and watering beyond the root zone are eliminated, substantial water and nutrient savings are realized. In addition, drip irrigation reduces contaminants to the water table by enabling the farmer to supply only enough water and fertilizer to reach the plants, reducing excess water that would run off and contaminate the water table below.
Emitters are used to control the flowrate of the water exiting the hose. Emitters can be located within the hose (internal emitters) or on the outside of the hose (external emitters). Generally, external emitters comprise a barb that punctures and extends through the wall of the hose. The barb contains an internal passage to provide a means for water to pass from the inside of the hose into the emitter. Such emitters are generally awkward due to the relatively large bumps protruding from the side of the hose, making it more difficult to roll the hose. Additionally, these emitters are subject to damage during initial installation and tend to break off. Moreover, if a broken or clogged emitter is removed and replaced with a new emitter, the hole into which the barb extends tends to stretch, increasing the likelihood of leaks. Further, due to the barb extending inside the hose, the water is subject to friction loss inside the hose. Thus, a need exists for a trouble-free emitter that overcomes these drawbacks.
Additionally, drip irrigation hoses tend to be relatively long to be able to extend across a field. As the water travels along the hose away from the water source, the pressure of the water decreases. Thus, the water pressure at the beginning of the hose (near the water source) is greater than that at the far end of the hose. Because the drip rate of the hose is a function of the water pressure, the drip rate at the beginning of the hose tends to be greater than at the end of the hose. The drip flow rate of such a hose is proportional to the water pressure at the inlet to the emitters raised to the exponent x. In the absence of pressure compensation, the x-factor is one, i.e., the flow rate is a linear function of the pressure. In the ideal case of perfect pressure compensation, the x-factor is zero, i.e., the flow rate is independent of pressure. Thus, the x-factor is a measure of the degree of pressure compensation--the lower the x-factor, the greater the pressure compensation. Generally, a hose having an x-factor of about 0.5 is considered to be somewhat pressure-compensating. A hose having an x-factor of 0.1 is considered highly pressure-compensating. Thus, it is desirable to incorporate pressure-compensating designs into the hoses to reduce the effect of the pressure difference over the length of the hose on the drip rate along the length of the hose.
Further, emitters tend to get clogged or plugged by dirt and other debris that finds its way into the emitter. Once the emitter is clogged, few practical alternatives exist for purging or clearing out the debris so that adequate water flow to the plant can resume. The farmer must often discard and replace the existing emitter or insert another near the plugged one, which can be very labor-intensive and expensive. Thus, a need exists for an external emitter that provides the farmer or other user with a simple way to unplug any debris.